Double parallelogram linkage lift

ABSTRACT

A lift including a base for support from a support surface, a generally horizontal load platform and a pair of parallel arms pivotally connected at one pair of corresponding ends to said base and at the other pair of corresponding ends to the load platform. Motor structure is connected between the base and the parallel arms for swinging the latter relative to the base and thus between arms and the platform for swinging the latter relative to the arms in a manner maintaining the platform generally horizontally disposed throughout swinging movement of the arms relative to the base and the platform relative to the arms.

United States Patent 1 I Stucky et al.

[ 1 Oct. 30, 1973 DOUBLE PARALLELOGRAM LINKAGE LIFT [22] Filed: Dec. 9, 1971 [21] Appl. No.: 206,458

[52] US. CL; 182/2, 182/63, 182/141 [51] Int. Cl. E04g 1/22, E04g 1/34- [58] Field of Search 182/2, 63, 141, 148

[56] References Cited UNITED STATES PATENTS 3,283,850 11/1966 Jones et al. 182/2 8/1968 Strom ..182/2 Primary Examiner-Reinaldo P. Machado Attorney-Harvey B. Jacobson [57] ABSTRACT A lift including a base for support from a support surface, a generally horizontal load platform and a pair of parallel arms pivotally connected at one pair of corresponding ends to said base and at the other pair of corresponding ends to the load platform. Motor structure is connected between the base and the parallel arms for swinging the latter relative to the base and thus between arms and the platform for swinging the latter relative to the arms in a manner maintaining the platform generally horizontally disposed throughout swinging movement of the arms relative to the base and the platform relative to the arms 7 4 Claims, 5 Drawing Figures PAIENTEDBU 30 mm 3.768, 591

SHEET 2 SF 3 Fig.2

' 1 DOUBLE PARALLELOGRAM LINKAGE LIFT The lift of the instant invention has been primarily designed for support from the load bed of trucks. However, the lift may also be utilized in other environments wherein a load platform is to be elevated while the platform is maintained in a generally horizontally disposed position.

The lift of the instant invention not only provides relatively simple structure for elevating a load platform, but an assemblage of component parts enabling substantially vertical elevation of the load platform while the latter is maintained horizontal.

There are many forms of truck mounted lifts or scaffolds which may be elevated from a lower position while the platform portion of the lift is maintained in substantially horizontal disposition. Two lifts or scaffolds of this type are disclosed in U.S. Pats. Nos. 3,283,850 and 3,472,337. However, these prior lifts or collapsible scaffolds include load platforms which are swung through an arc during the elevation and lowering processes. While load platforms elevatable in this manner serve many functions, in numerous instances it is desirable that such an elevatable platform be elevated along a substantially vertical path.

Accordingly, it is the main object of this invention to provide a lift assembly including a load platform supported from its base through a plurality of linkages and which may be moved from a loweredposition to an elevated position along a substantially vertical path.

Another object of this invention, in accordance with the immediately preceding object, is to provide a lift platform assembly including only pivotal connections between the relatively movable components thereof,

except for the fluid motors, and which thereby eliminates'sliding connections between relatively movable components.

Yet another object of this invention is to provide a scaffold or lift construction including an elevatable support or load platform enjoying a stable connection with the lifting structure therefor when the platform is in its elevated position.

A final object of this invention to be specificallyenumerated herein is to provide a lift assembly in accordance with the preceding objects which will conform to conventional forms of manufacture, be of simple construction and easy to use so as to provide a device that will be economically feasible, long lasting and relatively trouble free in operation.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout and in which:

FIG. 1 is a side elevational view of the lift assembly of the instant invention with the load platform thereof illustrated in a lowered position and the lift assembly mounted on the load bed of a pickup truck, portions of the pickup truck being'broken away and illustrated in vertical section;

FIG. 2 is a side elevational view similar to FIG. 1 but with the load platform of the lift assembly shown in an elevated position;

FIG. 3 is a top plan view of the assemblage illustrated in FIG. 1; I

FIG. 4 is a rear elevational view of the assemblage illustrated in FIG. 1; and

FIG. 5 is a schematic view of the hydraulic system by which the load platform of the lift may be raised and lowered while being maintained in a substantially horizontal position and being moved along a substantially vertical path.

Referring now more specifically to the drawings the numeral 10 generally designates a pickup truck including a load bed 12 having upstanding opposite sides 14 and 16.

The lift assembly of the instant invention is referred to in general by the reference numeral 18 and includes a base frame referred to in general by the reference numeral 20 positioned on the load bed 12 between the sides 14 and 16. The base frame 20 includes a forward generally rectangular and transversely extending frame section 22 having a lower rearwardly projecting foot or base 24 at its lower end. In addition, the base frame 20 includes a pair of opposite side diagonal brace members 26 secured at their upper ends to the opposite sides of the upper portion of the frame section 22 and interconnected at their lower rear ends by means of a horizontal transverse brace member 28. The transverse brace member 28 rests upon the load bed 12 and the brace member 28 as well as the base 24 may be secured to the load bed 12 in any convenient manner, if desired.

The upper ends of the opposite side members 30 of the frame section 22 include rearwardly projecting mounting flanges 32 and a first pair of parallelogram arm assemblies referred to in general by the reference numerals 34 are pivotally secured to the mounting flanges 32 as at 36. Each arm assembly 34 extends in a front to rear direction relative to the truck 10 and include upper and lower parallel arms 38 and 40 interconnected by means of vertical braces 42 and 44 pivotally secured at their opposite ends to the adjacent arms 38 and 40. The forward ends of the arms 38 and 40 are attached to the mounting flanges 32 at 36 and a second pair of parallelogram arm assemblies referred to in general by the reference numerals 46 and including upper and lower parallel arms 48 and 50 as well as vertical braces 52 and 54 corresponding to the braces 42 and 44 have the rear ends of their arms 48 and 50 pivotally secured to the rear ends of the arms 30 and 40 as at 56 and 58. i

A pair of fluid motors have their cylinder portions 72 pivotally secured to a pair of braces 74 mounted at the juncture of the opposite sides of the frame section 22 with the base 24 as at 76. The free ends of the piston rod portions 78 of the fluid motors 72 are pivotally secured to the arms 40 as at 80. In addition, a second pair of fluid motors 82 have their cylinder portions 84 pivotally secured to the rear ends of the parallelogram arm assemblies 34 and the free ends of their piston rod portions 86 pivotally secured to the arms 48 of the parallelogram arm assemblies 46 as at 88. Accordingly, upon extension of the fluid motors 70 and 82 the support platform 60 may be elevated from the lowered position thereof illustrated in FIG. 1 to the elevated position illustrated in FIG. 2.

From FIG. 5 of the drawings, it may be seen that the cylinders 70 include inlet and outlet fittings or ports 90 and 92 and that the fluid motors 82 include inlet and outlet ports 94 and 96. A reservoir 98 of fluid is provided as is a motorized pump 100 and a manually controllable valve 102. A supply line 104 leads from the reservoir 98 to the pump 100 and a main pressure line 106 extends from the outlet of the pump 100 to the inlet of the valve 102.

It will be also noted that a return line 108 extends from an outlet port 110 of the valve 102 to the reservoir 98. Pairs of supply and return lines 112 and 114 extend from the valve 102 to the inlet ports 90 and 96 of the cylinders 70 and 82, respectively. In addition, a line 116 having branches 116 communicates the ports 92 of the cylinders 70 with ports 94 of the cylinders 82. In operation, and with the understanding that the piston portions (not shown) of the cylinders 70 and 82 are disposed between the ports 90, 92 and the ports 94, 96 if it is desired to raise the platform 60 the valve 102 is actuated whereby the discharge from the pump 100 will be passed into the line 112 and behind the pistons within the cylinders 70. The fluid ahead of the pistons in the cylinders 70 will then of course be discharged from the latter as the piston rod portion 78 is extended and admitted into the cylinder portions 84 behind the pistons disposed therein in order to also extend the piston rod portion 86. The fluid ahead of the pistons of the piston rod portions 86 is of course discharged through the port96 and into the line 114 to be returned to the reservoir 98 through the valve 102 and the line 108. Then, when it is desired to lower the support platform 60, the valve 102 is actuated to vent the line 112 to the I line 108 and communicate the line 106 with the line 114 whereby the cylinders 70 and 82 will be caused to contract. It will be noted that the diameter of the cylinder portions 72 is less than the diameter of the cylinder portions 84. Therefore, the cylinders 70 and 82 will be extended and retracted at different rates. The rates of expansion and contraction of the cylinders 70 and 82 will be predetermined according to the relative angulation of the arm assemblies 34 and 46 when in the lowered and raised positions of FIGS. 1 and 2, respectively. This assures that the support platform 60 will be maintained substantially horizontal at all times and will be moved through a substantially vertical path during its movement from its lowered position of FIG. 1 to its elevated position of FIG. 2.

As herein set forth, the base frame including the base 24 and the transverse base 28 may merely rest upon a load bed 12 or removably secured thereto in any convenient manner.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and 4 equivalents may be resorted to, falling within the scope of the invention.

What is claimed is:

1. In combination, a lift including a base for positioning on a support structure, a generally horizontal elongated load platform including first and second end portions and first and second pairs of horizontally spaced apart opposite side parallelogram arm assemblies extending along opposite side portions of said platform and including corresponding first and secondend portions and upper and lower parallel arm members and supporting said load platform from said base, the first pair of parallelogram arm assemblies being pivotally connected at said first end portions thereof to opposite side portions of said base and at their second end portions to opposite side portions of the corresponding end of said load platform, the second pair of parallelogram arm assemblies extending longitudinally along opposite side portions of said platform and being secured to the latter, the second end portions of said first and second pairs of arm assemblies being pivotally secured together, first extendible motor means connected between said base and said first end portions of said first aim assemblies for swinging the latter relative to the former and second extendiblemotor means connected between said second end portions of said first arm assemblies and said second arm assemblies for swinging the latter, and said load platform, relative to the first arm assemblies in a manner maintaining the platform generally horizontal throughout swinging movement of said first arm assemblies relative to the base.

2. The combination of claim 1 wherein said first and second motor means includes first and second fluid motors having fluid inlets and outlets connected in series within a fluid pressure flow path extending from a source of fluid under pressure and returning back to said source. I

3. The combination of claim 2 wherein said first and second fluid motors, each includes a fluid inlet and a fluid outlet port disposed on opposite sides of the associated piston, said fluid flow circuit including a pressure line communicating the outlet port of said first cylinder with the inlet port of said second cylinder, a flow reversing control valve having pairs of inversely operable pressure outlet and fluid return ports, and second and third pressure lines communicating the inlet port of said first cylinder and the outlet port of said second cylinder with said valve ports.

4. The combination of claim 1 wherein said first pair of parallelogram arm assemblies are inclined downwardly when said platform is in a lowered position. 

1. In combination, a lift including a base for positioning on a support structure, a generally horizontal elongated load platform including first and second end portions and first and second pairs of horizontally spaced apart opposite side parallelogram arm assemblies extending along opposite side portions of said platform and including corresponding first and second end portions and upper and lower parallel arm members and supporting said load platform from said base, the first pair of parallelogram arm assemblies being pivotally connected at said first end portions thereof to opposite side portions of said base and at their second end portions to opposite side portions of the corresponding end of said load platform, the second pair of parallelogram arm assemblies extending longitudinally along opposite side portions of said platform and being secured to the latter, the second end portions of said first and second pairs of arm assemblies being pivotally secured together, first extendible motor means connected between said base and said first end portions of said first arm assemblies for swinging the latter relative to the former and second extendible motor means connected between said second end portions of said first arm assemblies and said second arm assemblies for swinging the latter, and said load platForm, relative to the first arm assemblies in a manner maintaining the platform generally horizontal throughout swinging movement of said first arm assemblies relative to the base.
 2. The combination of claim 1 wherein said first and second motor means includes first and second fluid motors having fluid inlets and outlets connected in series within a fluid pressure flow path extending from a source of fluid under pressure and returning back to said source.
 3. The combination of claim 2 wherein said first and second fluid motors, each includes a fluid inlet and a fluid outlet port disposed on opposite sides of the associated piston, said fluid flow circuit including a pressure line communicating the outlet port of said first cylinder with the inlet port of said second cylinder, a flow reversing control valve having pairs of inversely operable pressure outlet and fluid return ports, and second and third pressure lines communicating the inlet port of said first cylinder and the outlet port of said second cylinder with said valve ports.
 4. The combination of claim 1 wherein said first pair of parallelogram arm assemblies are inclined downwardly when said platform is in a lowered position. 